Abrasive-jet systems are used in precision cutting, shaping, carving, reaming, and other material-processing applications. During operation, abrasive-jet systems typically direct a high-speed jet of fluid (e.g., water) toward a workpiece to rapidly erode portions of the workpiece. Abrasive material can be added to the fluid to increase the rate of erosion. When compared to other material-processing systems (e.g., grinding systems, plasma-cutting systems, etc.), abrasive-jet systems can have significant advantages. For example, abrasive-jet systems often produce relatively fine and clean cuts, typically without heat-affected zones around the cuts. Abrasive-jet systems also tend to be highly versatile with respect to the material type of the workpiece. The range of materials that can be processed using abrasive-jet systems includes very soft materials (e.g., rubber, foam, leather, and paper) as well as very hard materials (e.g., stone, ceramic, and hardened metal). Furthermore, in many cases, abrasive-jet systems can execute demanding material-processing operations while generating little or no dust or smoke.
In a typical abrasive-jet system, a pump pressurizes a fluid to a high pressure (e.g., 275 meganewtons/square meter (40,000 pounds/square inch) to 689 meganewtons/square meter (100,000 pounds/square inch) or more). Some of this pressurized fluid is routed through a cutting head that includes an orifice element having an orifice. Passing through the orifice converts static pressure of the fluid into kinetic energy, which causes the fluid to exit the cutting head as a jet at high speed (e.g., up to 762 meters/second (2,500 feet/second) or more) and impact a workpiece. The orifice element can be a hard jewel (e.g., a synthetic sapphire, ruby, or diamond) held in a suitable mount. In many cases, a jig supports the workpiece. The jig, the cutting head, or both can be movable under computer or robotic control such that complex processing instructions can be executed automatically.
Some conventional abrasive-jet systems mix abrasive material and fluid to form slurry before forming the slurry into a jet. This approach can simplify achieving consistent and reliable incorporation of the abrasive material into the jet, but can also cause excessive wear on internal system components as the slurry is pressurized and then formed into the jet. In an alternative approach, abrasive material is mixed with a fluid after the fluid is formed into a jet (e.g., after the fluid passes through an orifice). In this approach, the Venturi effect associated with the jet can draw the abrasive material into a mixing region along a flow path of the jet. When executed properly, this manner of incorporating abrasive material into a jet can be at least partially self-metering. For example, replenishment of abrasive material in the mixing region can automatically match consumption of abrasive material in the mixing region. The equilibrium between replenishment and consumption, however, can be sensitive to variations in the source of the abrasive material upstream from the mixing region. In at least some cases, conventional apparatuses that convey abrasive materials within abrasive-jet systems insufficiently facilitate consistent and reliable delivery of abrasive materials to cutting heads. This can lead to variability in incorporation of the abrasive materials into fluid jets passing through the cutting heads, which, in turn, can cause skip cutting in metals, cracking and chipping in glass, delamination in composites, and/or other undesirable material-processing outcomes.